A University of Iowa study confirms that pathological gambling runs in families and shows that first-degree relatives of pathological gamblers are eight times more likely to develop this problem in their lifetime than relatives of people without pathological gambling.

"Our work clearly shows that pathological gambling runs in families at a rate higher than for many other behavioral and psychiatric disorders," says Donald W. Black, psychiatry professor at the UI. "I think clinicians and health care providers should be alerted to the fact that if they see a person with pathological gambling, that person is highly likely to have a close relative with similar or the same problem. That is a teaching moment and they should probably encourage the patient to let their relatives know that help is available."

Pathological gambling—gambling that is serious enough that it becomes a clinical issue—is a major public health problem that affects between 0.5 and 1.5 percent of American adults at some point during their lives.

The UI study, which was the largest of its kind to date, recruited and assessed 95 pathological gamblers and 91 control subjects, matched for age, sex, and level of education, from Iowa, as well as 1,075 first-degree adult relatives of the study participants (first-degree relatives include parents, siblings, and children.) Based on interviews and proxy interview material, the research team determined a gambling diagnosis for every person in the study.

They found that 11 percent of the gambling relatives had pathological gambling themselves compared to 1 percent of the control relatives, which means that the odds are about eight times higher in gambling families for pathological gambling to run in those families compared to control families.

"People have always thought pathological gambling ran in families—anecdotal evidence certainly suggested it. But when you finally do a study like this, which is the largest of its kind, and come up with figures like this, it is quite striking," says Black, who was lead author of the study published in the March issue of the Journal of Clinical Psychiatry.

When the researchers repeated the analysis to focus on problem gambling—a larger group of people than those with the more narrowly defined pathological gambling—they found that 16 percent of relatives of the pathological gamblers were problem gamblers compared to 3 percent of relatives of controls.

The researchers also looked the relationships between pathological gambling and rates of other psychiatric and behavioral disorders among study participants and showed that relatives of pathological gamblers had higher rates of major depression, bipolar disorder, social anxiety disorder, substance use disorders, Post-traumatic stress disorder (PTSD), and antisocial personality disorder.

Using statistical methods the team developed algorithms to determine which disorders are potentially biologically related to the gambling.

They found that antisocial personality, social anxiety disorder, and PTSD were more frequent in the relatives of pathological gamblers independent of whether the relative also had pathological gambling.

"This suggests that pathological gambling may share an underlying genetic predisposition with those disorders," says Black, whose primary appointment is in the UI Carver College of Medicine.

This finding appears to confirm previous research and clinical observation suggesting that antisocial personality disorder could be biologically related to pathological gambling. However, Black was surprised by the connection between pathological gambling and social anxiety and PTSD connection.

"No one has ever published that and it's hard to know what to make of it yet," he says.

The study also confirmed that mood disorders like major depression and bipolar disorder, as well as substance abuse, are common in pathological gamblers, but the analysis suggests that this probably is not due to a shared underlying biologic predisposition.

"I think our findings should give impetus to neuroscientists who conduct molecular genetic studies to really pursue this," Black says. "Maybe this situation provides a better chance of finding genes that are linked to the gambling disorder, and maybe that would pave the way for improving our understanding of the genetic transmission in general for psychiatric disorders, particularly in the realm of addiction."

In addition to Black, the UI research team included William Coryell, Raymond Crowe, Brett McCormick, Martha Shaw, and Jeff Allen. The study was funded by a grant from the National Institute on Drug Abuse (DA021361).